Selecting system



Aug. 1o, 1943. M E. MO'HR 2,326,551

SELECTING SYSTEM Filed Feb. 8, 1941 III /N VEA/Tof? M. E. MOHR ATTOR/VE V Patented Aug. 10, 1943 OFFICE SELECTING SYSTEM Application February 8, 1941, Serial No. 377,998

14 Claims.

This invention relates to selecting systems and particularly to systems in which selections are made automatically in a group of lines, trunks or other electrical circuits.

An object of the invention is to increase the speed and certainty with which the lines, trunks,

circuits or other devices of -a group are rendered unselectable in response to the selection of one of them for use.

Another object is to utilize the inductive eiect of a common impedance to render all circuits of a group unselectable in response to the iiow of current resulting from the selection of one of them.

Another object is to cause the selection of one of a group of equivalent Circuits by operating a discharge tube individual thereto and to utilize the induc'tance of a common impedance element to render the tubes of all othercir-cuits ineffective.

Another object is to utilize both the inductance and resistance of the common element for preventing the selection of other circuits.

Other objects of the invention are to simplify, to increase the speed of operation, and otherwise to improve selecting systems,

These objects are realized by means of a selecting system in which a group of equivalent circuits, or other devices, from which selection is to be made is provided with a plurality of discharge tubes, one for each of the several circuits, together with means for causing the discharge of the tube individual to an idle circuit; and in which an inductive element common to all of the tubes responds to the flow of current, when any one of said tubes discharges, to produce a voltage change on the electrodes of all other tubes to prevent another one from discharging and selecting a second one of said circuits. More specincally this selecting system is so arranged that any one of the circuits may be chosen for use providing it is idle at the time selection is required. Tc this end potential is applied to the tubes of all idle circuits. Since, however, the individual characteristics of each tube differ somewhat from from those of the remaining tubes in the group, some one of the tubes repre- Santing idle circuits will be the rst to discharge. The instant discharge current ows, .the common inductance element produces a high'voltage drop Which is applied to the electrodes of all ltubes and which serves to disable any other tube tubes and prevents a second one from discharging. Thus it is possible to select one from a number of equivalent idle circuits and to insure against the undesirable selection of a second circuit.

A feature of the invention is a selecting system of the kind above mentioned in which the anodes of the selecting tubes are connected to each other vthrough a plurality of condensers. Whenever current flows in the discharge gap of one of these tubes', the Voltage -drop Vproduced by the work relay in the anode circuit causes charging current to flow in the condensers to reduce the voltage onthe anodes of all other tubes. Thus the voltage diiierence across the discharge gaps of all other tubes is reduced by the instantaneous Voltage drop produced in the common inductance element and by the voltage drop produced by the charging of the condensers connected to the anodes of said other tubes.

'Ihese and other features of the invention will be described more fully in the following detailed specication.

The drawing accompanying the specification discloses the invention when applied to a, switching system for connecting incoming circuits to any one of a group of equivalent outgoing circuits.

Although the invention is applicable to selecting and connecting systems in general and without regard to the specic purposes for which these systems are used, it is disclosed in the drawing in connection with the switches of a telephone system. One of these line switches |00, which may be of the well-known cross-bar type,Y serves to extend the calling subscribers lines |0|, |02, etc., to idle links or trunks |03, |04, |05, etc. Usually a plurality of these switches are assembled on a frame, and common controlling equipment is `provided for selecting and operating the horizontal and vertical magnets to determine the orderly extension of the calling lines to respective idle outgoing circuits. For a better understanding of the structure and operation of the cross-bar switch reference is made to the patent to Reynolds 2,021,329 of Novembery 19, 1935. As to the manner in which line switches of this type vare controlled, reference is made to lthe, patent to Busch et al. 2,224,251 of December Referring again to the drawing, the subscribers lines ll, |02, etc., appear respectively in the vertical rows of contacts in .the switch |00, and the outgoing lcircuits |03, |04, |05, etc., appear respectively in the horizontal rows of contacts in the switch. The subscribers lines are represented, respectively -by individual line relays |06, |01, etc., and also by the switch hold magnets |08, |08, etc. The outgoing circuits are represented respectively by the select magnets I 0, III, ||2, etc. The operation of any desired set of cross-point contacts in the switch is effected by energizing first the select magnet associated with the horizontal row containing thedesired set of contacts and then the hold magnet pertaining to the appropriate vertical row of contacts.

In addition to the usual select magnets of the switch a plurality of space dicharge tubes are provided, there being one of these tubes for each horizontal row of contacts, or one tube for each outgoing circuit. For example, the tube ||3 is associated with the outgoing circuit |03 and with the select magnet individual t0 this circuit, and the tubes ||4 and ||5 are individual respectively to the outgoing circuits |04 and |05. And i the same is true of the remaining tubes of the group not shown in the drawing. While these tubes may be of any suitable type, such as those filled with different gases, it has been found that much better results are obtained in the system disclosed herein when tubes filled with argon are employed. Tubes of this type having initial ionizing gaps and main discharge gaps are well known in the art. A starting voltage applied to the ionizing gap causes the initial ionization, which then transfers to the main discharge gap if an operating voltage of sufficient value is applied to the main gap. As soon as the main gap discharges, the voltage necessary to sustain this discharge drops to a value substantially lower than the initial operating voltage. These are Well-known characteristics of gasgfilled tubes.

The control or starting electrodes of the discharge tubes are connected respectively to the sleeve or test conductors of the associated circuits, the cathodes of all tubes are connected to a common conductor, and the anodes are connected respectively to the corresponding select magnets. For instance, the start electrode IIS of the tube I3 is connected to the test conductor ||1 of the circuit |03. Likewise the start electrodes ||8 and ||9 are connected respectively to the test conductors and |2| of outgoing circuits |04 and |05. The cathodes |22, |23 and |24 of all tubes in the group are connected by way of the common conductor |25 through the contacts of a control relay |26 through a common inductor and resistor 4|21 to the negative pole of battery |28. The anodes |29, |30, |3|, etc.` are connected to the corresponding select magnets ||0, ||2, etc. Each of thetube anodes is also connected to one terminal of a condenser, there being one of these condensers for each tube. 'Ihe other terminals of all condensers are joined together by a common conductor. For example, the anodes of tubes I3, ||4 and I I5 are connected to the associated condensers |32, |33 and |34, respectively. The purpose of the common element |21 connected to the cathodes and the individual condensers connected to the respective anodes of the tubes is, as will be explained more fully hereinafter, to prevent the simultaneous operation of two or more tubes and the false connections that would result therefrom The operation of the selecting system will now be described in detail. For this purpose it may be assumed that line |0| initiates a call and that circuits |03 and |04 are idle at the time, whereas circuit |05 is busy. When the subscriber of line |0| removes his receiver to make the call, an

obvious circuit is closed for energization of the line relay |06. Relay |06 closes an energizing circuit for the group relay |26. Relay |26 closes at its inner left contacts alcircuit for applying the full negative potential of battery |28 to the cathodes |22, |23, |24, etc., of all tubes. Since the circuit |03 is idle at this time, relay |35 is clinergized, and the positive potential ofv battery tube |13. Thus the voltage applied across the starting gap II6-I22 isthe sum of the voltages of batteries |28 and |36, which is suflicient to ionize saidV starting gap. Similarly, the relay |31 is deenergized, the circuit |04 being idle, and the positive potential of battery |38 is applied to the start electrode ||8 of the tube I4. Hence the voltage applied to the gap IIB-|23 is the sum of potentials of batteries |28 and |38, which likewise is sufficient to ionize said starting gap. Similarly ionizing voltage is applied to the starting gaps of all other tubes representing idle outgoing circuits. However, each busy circuit, such as the circuit |05, has ground potential applied to its test conductor, and the resulting voltage across the starting gap IIS-|24 is insufficient to produce ionization.

Since the several tubes of. the group are in- .herently different in their characteristics, the ionizing current in the control gap of some one r ohmic resistance.

of the tubes will reach the transfer value ahead of the remaining tubes. Assume, for example, that the ionizing current in the tube ||3 reaches the transfer value ahead of the remaining tubes, including tube I4. As soon as the transfer value is reached discharge to the main anode takes place, and current flows in a circuit which may be traced from the positive pole of battery |39, contact of relay |26, conductor |40, through the winding of select magnet ||0, anode |29, cathode |22, conductor |25, contacts of relay |26, element |21 to the negative pole of battery |28. It should be noted at this pointv that the inductive reactance of the impedance element 21 is preferably made high in comparison with its The high inductance of the element serves to produce a relatively high voltage when the initially small discharge currents first flow; while the low ohmic resistance of the element permits the subsequent fiow of the relatively heavy discharge currents after the inductive effect of the element has subsided. Due therefore to the inductance of the element |21 the first flow of current in the discharge circuit above mentioned produces a relatively high voltage across the element |21. 'I'he polarity of this voltage is such that a positive potential is applied instantly to the cathodes of the remaining tubes in the group. 'I'his positive potential when applied to the cathode |23 opposes the flow of ionizing current in the starting gap ||8|23 and also opposes the transfer of the discharge, which is about to occur, to the main anode |30. Thus the tube ||4 is prevented from discharging and causing the selection of a second one of the outgoing circuits. Similarly the induced voltage created by the inductor |21 prevents any other tube associated with an idle outgoing circuit from discharging and causing the false selection of such circuit.

As the inductive effect oi' element I 21 abates, the current in the discharge circuit above traced rises to its full operating value because of the.

relatively low ohmic resistance of element |21 and causes the energization of the select magnet ||0 to prepare the horizontal row of contacts in is applied to the start electrode ||6 of the l which the selected outgoing circuit |03 appears. Thereafter in any suitable manner a circuit is closed over conductor |4| for the operation of the hold magnet |08. The line is now connected to the outgoing circuit |03,relay |06 releases, and relay I26-releases to disconnect the batteries |28 and |39 from the tubes. Magnet |0 is released, and the connection is now held by the hold magnet |08 over a circuit traceable from battery through the winding of the magnet, closed contacts of the switch to ground potential which has been applied to the holding or test conductor Returning to the point where the rst tube, tube H3, transfers its/*ionization to the main anode, an explanation will now be given of the manner in which the condensers associated with the tubes serve with the inductor |2ll to prevent the discharge of a second tube. At the instant transfer takes place to the main anode |29 in tube H3, the individual terminals of condensers |32, |33, |34, etc. are at the full positive potential of battery |39. As soon, however, as current begins to iiow in the anode-cathode gap of the tube I I3 and through the winding of magnet |0 the positive potential on the terminal of condenser |32 is lowered by the amount of the voltage drop across the magnet |10. Hence the potential of the individual terminal of condenser |32 differs from the potential of the corresponding terminals of each of the other condensers, and the resulting voltage drop cau-ses charging current to iiow over circuits including these condensers and the windings of the select magnets. One of these circuits may be traced through condensers |32 and |33 and through magnets ||0 and in series. The voltage drop produced by the flow of charging current in the winding of magnet ill lowers the positive potential of the anode |30 by a corresponding amount, thus lowering still further the voltage applied across the anode-cathode gap |30|23. Therefore, the tube H6 is prevented from operating by the induced voltage produced by the inductor |2'i at the instant the first tube I3 operates and by the lowering ofthe potential on the anode |30 resulting from the charging current flowing in condensers |32 and |33. in like manner charging current iiows into each of the other condensers in series with the associated magnet, and the anode potential of the associated tube is lowered correspondingly.

After the current ow in the operated tube has reached the steady state the voltage drop across the common element |21 vdue to the resistance thereof maintains a potential on the cathodes of all other tubes such that no one of them can operate.

When it is desired to release the established connection through the switch |00, ground potential is removed from the sleeve conductor Ii'i, and magnet |08 deenergizes to restore the crosspoint contacts to their normal condition.

What is claimed is:

l. In combination, a plurality of selectable circuits, discharge devices individual respectively to said circuits, means for applying a potential to all of said devices to cause any one of them to discharge, means responsive to the current flowing in the discharged device for selecting the corresponding circuit for use, and inductive means responsive to the discharged device for changing the potential on the other discharge devicesto prevent the discharge of a second one thereof.

2. In combination, a plurality of selectable circuits, discharge devices individual respectively to said circuits. means for applying an operatingl charge devices to prevent a second one from op- 3. The combination in a selecting system oi. a plurality of selectable lines, discharge tubes individual respectively to said lines, each tube having a plurality of electrodes, means for applying a voltage across the electrodes of all tubes suiiicient to cause the operation of any one thereof, discharge circuits, one for each tube, means responsive to the flow of current in the discharge circuit of the first tube to operate for selecting the corresponding line for use, and an inductive element connected in common toan electrode of each of said tubes, said element responding to the current flowing injthe discharge circuit of the operated tube to cause an instantaneous reduction below the operating value of the voltage applied to all other tubes.

4. The combination in a selecting system of a plurality of selectable lines, discharge tubes associated respectively with said lines, each tube having an anode and a cathode forming a discharge gap, means for applying operating voltages simultaneously across the discharge gaps of all of said tubes, means responsive to the discharge current owing in the first tube to operate to select the corresponding line for use, and an inductor connected to all of said cathodes and responsive to the discharge current flowing in the operated tube for producing an instantaneous drop in the voltage across the gaps of all other tubes.

5. The combination in a selecting system of a plurality of selectable lines, discharge tubes associated respectively with said lines, each tube having an anode and a cathode forming a discharge gap, means for applying simultaneously operating voltages to the discharge gaps of the tubes corresponding to idle lines, means responsive to the discharge of the first tube to operate for selecting the corresponding line for use, and an inductor connected to all of said cathodes and responsive to the discharge of the operated tube for producing an instantaneous drop in the voltage across the gaps of the tubes associated with the remaining idle lines.

6. The combination in a selecting system of a plurality of lines, discharge tubes associated respectively with said lines, each tube having an anode and a cathode, an individual discharge circuit for each of said tubes, means for applying operating voltages simultaneously to said tubes, means responsive to the current flowing in the first tube to operate for selecting a corresponding line for use, an inductance element responsive to the current flowing in the operated tube for lowering the potential applied to the cathodes of the remaining tubes, and impedance elements connected respectively to said anodes and responsive to the current flowing in the operated tube for lowering the potential on the anodes of the remaining tubes, the lowered potentials of said cathodes and anodes serving to prevent the operation of a second tube.

7. The combination in a selecting system of a group of lines, a plurality of discharge tubes associated respectively with said lines, each of said tubes having an anode and a cathode, relays connected respectively to the anodes of said tubes, means for applying simultaneously operating voltages across the gaps formed by the anodes and cathodes of said tubes, the discharge current nowing in the rst tube to operate serving to energize the associated relay to' select the corresponding line ior use, an inductance element responsive to the discharge current flowing in the rst tube to operate for lowering the potential applied to the cathodes of the remaining tubes, and a plurality of condensers connected respectively to the anodes of said tubes, said condensers being charged in response to the discharge current ilowing in the first tube to operate to lower the potential applied to the anodes of the remaining tubes.

8. I'he combination in a selecting system of a cross-bar switch, a plurality of lines appearing in said switch, a plurality of discharge tubes individual respectively to said lines, a plurality of magnets for operating said switch to make connection with said lines, means for applying simultaneously operating voltages to said discharge A tubes to cause the discharge on any one thereo'f,

the current flowing in the rst tube to discharge serving to operate one of said magnets to select the. corresponding line for use, and inductive means connected to all of said tubes and responsive to the discharge current flowing in the first one to operate for lowering the voltage applied to all other tubes to prevent a second one from operating.

9. The combination in a selecting system of a plurality of selectable lines, discharge tubes asl sociated respectively with said lines, each tube having an anode and a, cathode forming a. discharge gap and an envelope filled with argon gas, means for applying operating voltages simultaneously across the discharge gaps of all of said tubes, means responsive to the discharge current flowing in the iirst tube to operate to select the corresponding line for use, and an inductor connected to all of said cathodes and responsive to the discharge current owing in the operated tube for producing an instantaneous drop in the voltage across the gaps of all other tubes.

10. The combination in a selecting system of a plurality of selectable lines, discharge tubes associated respectively with said lines, each tube having a main anode, a cathode and a starting anode, the cathode and starting anode forming an initial discharge gap, the cathode and main anode forming a main discharge gap, means for applying simultaneously operating voltages to the initial discharge gaps of a plurality of said tubes, means responsive to the discharge current flowing in the main discharge gap of the rst tube to operate to select the corresponding line for use, and an inductor connected in common in the initial discharge gaps of all of said tubes and responsive to the discharge current flowing in the initial gap of the rst tube to operate for producing an instantaneous drop in the voltage across the initial gaps of all other tubes to prevent the operation of a second one of the tubes.

11. The combination in a selecting system of a plurality of circuits, discharge tubes individual respectively to said circuits, each tube having a starting gap and a main discharge gap, a source of voltage, a. common supply conductor for supplying ionizing voltage from said source to the starting gaps of said tubes and for supplying operating current from said source to the main discharge gaps of said tubes, means responsive to the flow of current in the main discharge gap of an operated tube for selecting the corresponding circuit for use, and aninductive element connected in said 'supply conductor and responsive to the flow of current for ionizing the starting gap of any one of said tubes to produce an instantaneous drop in the voltage applied to the starting gaps of all other tubes.

12. The combination in a selecting system of a plurality of circuits, discharge tubes individual respectively to said circuits, each tube having a starting gap and a main discharge gap, a source of voltage, a common supply conductor for supplying ionizing voltage from said source to the starting gaps of said tubes and for supplying operating current from said source to the main discharge gaps of said tubes, means responsive to the ilow of current in the main discharge gap of an operated tube for selecting the corresponding circuit for use, and an impedance element included in said common supply conductor, said impedance element having a relatively high inductive reactance and responsive to the ilow of current in said common supply conductor for producing an instantaneous voltage to prevent the remaining tubes from operating, said impedance element having a relatively low resistance to permit the flow of a. relatively high current over said supply conductor and through the main discharge gap of the operated tube.

13. The combination in a selecting system of a plurality of selectable circuits, discharge tubes individual respectively to said circuits, each of said tubes having electrodes forming discharge gaps, each tube requiring a given voltage to cause ionization of its discharge gap and a substantially lower voltage to maintain the ionization, means for applying an operating voltage to all of said tubes, means responsive to the discharge current flowing in the rst one of said tubes to operate for selecting the corresponding circuit for use, and an inductive element responsive to the discharge current flowing in the operated tube for reducing the voltage applied to all of said tubes to a value below the ionizing voltage and above the sustaining voltage of the discharge gaps of said tubes.

14. The combination in a selecting system of a plurality of selectable circuits, discharge tubes individual respectively to said circuits, each of said tubes having electrodes forming discharge gaps, each tube requiring a given voltage to cause ionization of its discharge gap, means for applying an operating voltage to all of said tubes, said tubes having inherently different time intervals for eiecting discharge following the application of said operating voltage, means responsive to the discharge current flowing in the first one of said tubes to operate for selecting the corresponding circuit for use, and an inductive element responsive to the discharge current ilowing in the operated tube for reducing the voltage applied to the remaining tubes before a second one of said tubes succeeds in operating.

MILTON E. MOI-IR. 

